(function (doc, win) {
  var docEl = doc.documentElement,
     resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
     recalc = function () {
         var clientWidth = docEl.clientWidth;
         if (!clientWidth) return;
         if(clientWidth>=750){
             docEl.style.fontSize = '100px';
         }else{
             docEl.style.fontSize = 100 * (clientWidth / 750) + 'px';
         }
     };

if (!doc.addEventListener) return;
 win.addEventListener(resizeEvt, recalc, false);
 doc.addEventListener('DOMContentLoaded', recalc, false);
})(document, window);
